THE ENERGY INDUSTRY TIMES - JUNE 2018 Special Project Supplement Kozienice 11 marks a new era in coal fired generation Kozienice 11 is Poland’s most modern and efficient coal fired station. Its start up highlights the country’s commitment to building coal fired power plants that can operate at efficiencies of higher than 45 per cent while meeting the EU’s latest environmental standards. Junior Isles of 620°C. The steam turbine is state-of-theart, combining advanced 3-D blading and improved blade tip seal technology for high steam turbine efficiency. The steam turbine and generator are manufactured in Japan. Notably, only ferritic steel made in Japan is used, as opposed to austenitic steel. Japanese manufacturers have the longest experience with this steel. MHPSE says this has some key advantages. Combining a ferritic steel rotor with austenitic steel blades can cause problems in the long term due to the different rates of thermal expansion. MHPSE says it can handle the 600°C temperature with just ferritic steel. The development of high-temperature resistant steels in Japan was an essential key to building this new generation of highly efficient ultrasupercritical power plants. The economy of ultra-supercritical (USC) power plants depends on reliable evidence of their long-term strength. Japan has a great deal of experience in operating USC steam power plants, with references that demonstrate high reliability since 1998 with live steam temperatures of 600°C and reheat temperatures of 610°C to 620°C. The low-pressure section is where the steam turbine has its greatest innovation. It is the first time in Europe that a 60-inch last stage blade is used in the low-pressure turbine. The largest is currently 49 inches. With this new last-stage blade, the cooling water temperature of 17°C and a vacuum of 40 mbar can be utilised in the steam turbine at quite moderate steam turbine exhaust velocities, which results in higher plant efficiency. The large cooling tower also helps to maximise efficiency at the site. Because the plant is located next to a river in the middle of the country, the cooling water conditions are not as favourable as if the plant was located next to the sea with direct seawater cooling. Consequently, not only is the cooling water warmer than if it came directly from the sea but also there is a constraint on the amount of available cooling water. At 185 m high, the cooling tower is one of the tallest in Europe. This has a direct positive impact on the efficiency of the plant. The cooling is a closed circuit where the water in the cooling tower can reach 33°C. The cooling water from the tower is used to cool the condensate in the condensers. The plant’s design not only limits A site on the banks of the Wistula River, 60-70 km southeast of Warsaw, is now home to the largest, most efficient, coal fired power plant in Poland and among the most efficient in the world. Kozienice 11, located in Swierze Górne near Kozienice, was officially handed over to Polish state-controlled energy company, Enea, on December 19, 2017, marking the culmination of four years of a huge collaborative effort between its constructors – Mitsubishi Hitachi Power Systems Europe (MHPSE), its Polish consortium partner Polimex-Mostostal S.A. and several Polish authorities. While coal fired plants might be a dying breed in Europe and the US, some argue that the project shows that coal can still play a role in some parts of the world and can provide affordable, reliable electricity, while keeping emissions well below strict environmental limits. Poland has long been an ardent supporter of coal fired generation. It has the largest reserves of coal in the EU and uses the fuel for about 90 per cent of its electricity. It currently has 3.2 GW under construction – all scheduled to come online throughout the next decade – part of a 10 GW build-out of new coal fired power generating capacity in the country. The new Kozienice 11 power unit will strengthen Poland’s coal-based electricity production, which is in line with its policy of “focusing on one’s own resources”, promoted by Poland in the EU. According to the government, this strategy significantly raises Poland’s energy security, which it sees as a part of its national and economic security. With the construction of Kozienice 11, MHPSE played an important role in the extension of the Polish power generation system and in ensuring a dependable supply of electricity in an expanding economy. Construction of the new unit itself also provided a boost to the local economy. While MHPSE was responsible for delivering all the major equipment, the entire balance-ofplant, HV electricals, civil works and construction was handled by Polimex-Mostostal. At a total cost of zlotys 6.3 billion (€1.5 billion), Kozienice 11 is one of the biggest energy investments in Poland. About half of the contract value was handled by the domestic consortium partner – fulfilling a legal requirement that local partners must be involved in such projects. According to MHPSE, the proviso had its advantages, noting that there are issues such as Polish civil law for construction that are typically better handled by local companies. Also, with the contract being paid in Polish zlotys, it was advantageous to have a significant portion of the supply in zlotys. The most important components for the new unit were either supplied by companies within the corporate group or from parent company Mitsubishi Hitachi Power Systems, Ltd. (MHPS). These include the steam generator, coal bunkers, coal mills, firing equipment, flue gas cleaning, and some balance-of-plant. MHPS supplied the steam turbine, generator, auxiliary equipment and the flue gas desulphurisation (FGD) plant. The new unit is part of an existing site, where there were already 10 units with a generating capacity of 2905 MW. It is an important facility – it is the second largest in the country, after Belchatow, and represents The new Kozienice 11 power unit will strengthen Poland’s coal-based electricity production, which is in line with its policy of “focusing on one’s own resources” 8 per cent of the country’s installed capacity. Notably, it is the first coal fired power station in Poland designed to have an efficiency of nearly 46 per cent and follows a list of supercritical coal fired plants, like those seen in Germany and the Netherlands. Kozienice 11 has a net generating capacity of 1000 MW and is hooked into both the 110 kV and 400 kV grids, and controlled remotely from a control centre in Warsaw some 70-80 km away. Using an existing site for the new highly efficient Unit 11 was an obvious choice. In addition to the infrastructure, the site is next to the Wistula River, which provides the cooling water to feed the huge cooling tower. The plant receives bituminous coal by rail from all over the country. Although it is designed to burn Polish coal, it can run on coal from elsewhere if necessary. Coal arriving at the plant is typically high volatile bituminous coal with a calorific value of about 20 000 - 24 000 kJ/kg, ash content of 16-25 per cent and sulphur content of around 0.8 - 1.3 per cent. Coal is fed by conveyor belt to the plant where it is first crushed to a fine powder by a series of mills before being fed into the boiler at a rate of 101.9 kg/s (guarantee coal). Four mills are located at the bottom of the boiler, which MHPSE says is quite unusual for a boiler of this size. There are typically 6-8 mills for a boiler this size but Kozienice 11 uses four large mills. The boiler, which has a gross maximum power output of 1075 MW, measures 104 m at its highest point. Unlike a two-pass boiler, which is more common in places like the UK or US, Kozienice 11 features a tower-type boiler where the convective heat section is above the radiant section of the boiler. The convective heating surface is above of the evaporator. The boiler features 32 wall-fired, internally-staged low NOx burners – eight burners situated on four levels inside the boiler. Supercritical steam conditions within the boiler are the main contributor to the plant’s high efficiency. The once-through Benson design steam generator produces 2894 t/h steam with a superheated steam reheat temperature of 603°C at 250 bar and reheat steam at 621°C/55 bar. According to MHPSE, the 603°C/250 bar is quite unique for Europe. Although the temperatures are similar to other supercritical projects in Europe, the pressures are usually 20-30 bar higher. Supercritical steam conditions represent a physical point just above the triple point of water. When the boiler pressure reaches above the critical pressure of 221.2 bar and temperature of 374°C, two-phase mixtures of water and steam cease to exist, and are replaced by a single supercritical fluid. These steam conditions allow a once-through boiler design where the high steam temperature and pressure results in greatly increased efficiency compared to a drum-type boiler. Supercritical steam is fed to an advanced four-casing steam turbine of dual shell design. There is a highpressure (HP) turbine, a double-flow intermediate-pressure (IP) turbine and two double-flow low-pressure (LP) turbines. The LP end of the turbine is connected to a hydrogencooled generator. Steam pressure at the turbine inlet is 242 bar with main steam temperature of 600°C and reheat temperature
Energy Industry Times June 2018
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